The present invention relates to a method of producing an elongate sheet of material that includes barrier flaps which extend along the side-edges of said sheet in spaced relationship with said side-edges and which project up from the plane of said sheet.
Liquid absorbent articles, such as diapers, provided with elongate elastic elements for imparting a desired shape to the article in its use state are known to the art. In the case of diapers and incontinence protectors, which in use are donned by the wearer in a pants-like configuration, it is usual to provide so-called leg elastic which extends along the side-edges of the diaper in the crotch region thereof, so as to create, when the diaper is donned, raised elastic edges which seal tightly around the thighs of the wearer, such as to enclose discharged body liquid, or fluid, in the diaper.
It is also known to provide longitudinally extending, raised barrier flaps on the liquid receiving surface of absorbent articles. These barrier flaps function to prevent liquid flowing laterally out towards the side-edges of the article and leaking over said side-edges. Such barrier flaps are particularly effective, when the wearer lies on one side or when the wearer discharges large volumes of liquid at one and the same time. The barrier flaps also prevent lateral spreading of faeces. The barrier flaps can either be used alone or together with leg elastic.
It is known, e.g., from EP 0 391 476 to provide a diaper with raised barriers. These barriers are folded down against the absorbent body in their respective crotch centre sections and are glued in this position. This results in raised barriers whose height above the absorbent body in the crotch region is lower than the height above respective rear and front parts of the diaper, which is said to enhance wearer comfort. It is also said that the main purpose of the barriers is to provide a damming effect, whilst the actual seal against lateral leakage is comprised of the leg elastic.
U.S. Pat. No. 5,413,570 teaches another method of obtaining raised barrier flaps, which in this case are fastened on top of the outer material of the diaper. These flaps have a long-edge part which is fastened to the diaper, and a long-edge part which is free. The fastened edge-parts of the barrier flaps may be straight, whereas the free edge-parts may be curved and provided with elastic elements. Alternatively, the barrier flaps may consist of strips of uniform widths and which have been attached to the diaper with a curvature that converges towards or diverges away from the crotch section.
EP 0 374 640 teaches an alternative method of providing raised barrier flaps of varying heights. The front end-parts of the barrier flaps, which are straight originally, are folded towards the centre of the diaper and fastened thereto, whereas the rear end-parts of the flaps are folded back against the rear outer corner-parts of the diaper and there fastened. Each flap will therewith be folded towards the centre of the diaper at its front edge and out from the centre of the diaper at its rear edge.
One problem with the manufacture of absorbent articles of the aforesaid kind resides in producing raised barrier flaps on an outer sheet of such a product in a simple and cost-effective manner.
An object of the present invention is to solve this problem and, at the same time, provide a sheet of material that includes barrier flaps where the material in that part of the sheet lying between the flaps and in the parts of said sheet that lie laterally outside said flaps, and the material in the barrier flaps can be freely chosen.
This object is achieved with a method of producing an elongate sheet that includes barrier flaps which extend along the side-edges of the sheet in spaced relationship with respective side-edges, and which project up from the plane of said sheet, said method being characterised by the steps of
placing along each edge-part of a first elongate sheet of material a second elongate sheet of material whose width is smaller than the width of the first sheet, such that the outer side-edges of respective second sheets will lie edge-to-edge with the side-edges of the first sheet;
placing along each edge-part of the first elongate sheet and on top of respective second sheets a third elongate sheet whose width is smaller than that of the first sheet, such that the outer side-edges of respective third sheets will lie edge-to-edge with the side-edges of the first sheet and the second sheets;
joining the first, second and third sheets together with a join that extends along the outer side-edges of said sheets; and
swinging the third sheets laterally outwards through an angle of 180xc2x0 around their join lines and laterally stretching the sheet composite consisting of the mutually joined first, second and third sheets, therewith raising the second sheets from the plane of the first and third sheets. Such a process can be readily incorporated in a continuous absorbent article manufacturing process without having a disturbing effect on the remainder of the process and without needing to slow down production. The equipment required to carry out the method is both simple and uncomplicated. The method thus enables barrier-carrying outer sheets to be produced in a cost-effective manner. Because the first, second and third sheets are mutually separate sheets, the materials from which these sheets are comprised may be freely chosen.
In one preferred embodiment, the second sheets are comprised of elastic material and are applied in a stretched state. In one variant, the second sheets are shorter in length than the first and third sheets, said first and third sheets comprising continuous webs of material and the second sheets being applied in pairs on the first sheet with said pairs of second sheets being spaced at a given distance apart The end-edges of the second sheets are joined to the first sheet prior to the third sheets being applied, and the various sheets are joined together by heat welding or ultrasonic welding, or are glued together.
The invention also relates to an elongate, liquid-permeable outer sheet for absorbent articles, such as diapers, incontinence protectors and sanitary napkins, said outer sheet including barrier flaps which extend along the side-edges of said sheet, at least within a longitudinal central part thereof, in spaced relationship with respective side-edges, and which project up from the plane of said sheet, said sheet being characterised in that the barrier flaps, the part of the sheet that lies between said barrier flaps, and the edge-part of the sheet lying laterally outside the barrier flaps are comprised of mutually separate and mutually joined sheets of material.
That part of the outer sheet which lies between the barrier flaps is comprised of liquid permeable material, whereas the edge-parts and the barrier flaps are comprised of liquid impermeable material. The barrier flaps are comprised of elastic material, or material that has been made elastic, and extend along the full length of the outer sheet.
In one variant, the end-edge of the barrier flaps are spaced longitudinally from respective end-edges of said sheet, and the end-edges of the barrier flaps are fastened to that part of the sheet which lies between said barrier flaps.
It will be understood that by xe2x80x9celastic materialxe2x80x9d is meant a material that can be stretched and that strives to return to its original form when the stretching load is removed.